Refractive index(n(ω)) calculation: Kramers-Kronig relations

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Discussion Overview

The discussion revolves around the calculation of the refractive index from experimental spectral data using Kramers-Kronig relations (KKR). Participants are seeking advice on methods and software, particularly MATLAB and Origin, to effectively implement these calculations.

Discussion Character

  • Technical explanation
  • Homework-related
  • Debate/contested

Main Points Raised

  • One participant expresses difficulty in calculating the refractive index using KKR and requests expert advice, specifically mentioning familiarity with MATLAB and Origin.
  • Another participant suggests using the Fourier transform method to evaluate Hilbert transforms, noting that the Kramers-Kronig transform is essentially a Hilbert transform and mentions a MATLAB function for this purpose.
  • A participant confirms the relationship between KKR and Hilbert transforms, indicating that a complex program is unnecessary for KKR in MATLAB.
  • One participant requests details on the steps taken to solve similar problems, indicating they have n and k values and want to extrapolate to higher and lower energies using KKR.
  • A different participant raises concerns about the challenges of using KKR with limited spectral data, particularly regarding errors from finite spectrum integration, and seeks clarification on using Hilbert transforms in MATLAB.
  • Another participant expresses frustration about not being able to manage refractive index calculations after applying the Hilbert transform to absorption data.
  • One participant humorously notes that providing detailed programming assistance is part of their professional work, implying limitations on sharing comprehensive solutions freely.

Areas of Agreement / Disagreement

Participants generally agree on the relevance of Hilbert transforms to KKR but express differing levels of success and understanding in applying these methods. There is no consensus on a specific solution or approach to the problem.

Contextual Notes

Participants mention limitations related to finite spectral data and the potential for errors in integration, as well as varying levels of familiarity with the necessary software tools.

Who May Find This Useful

This discussion may be useful for researchers or students working on optical properties of materials, particularly those interested in the application of Kramers-Kronig relations and Hilbert transforms in data analysis.

ddhirhe
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I try to calculate refractive index of experimental spectral data using Kramers-Kronig relations but didn’t succeed. I need your expert advice and help to solve this problem.
Data and expression for KK relation is give in worksheet, where alpha(omwga) is in cm-1. Solution through Matlab or Origin is more helpful for me since I am familiar with this two software.
 

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ddhirhe said:
I try to calculate refractive index of experimental spectral data using Kramers-Kronig relations but didn’t succeed. I need your expert advice and help to solve this problem.
Data and expression for KK relation is give in worksheet, where alpha(omwga) is in cm-1. Solution through Matlab or Origin is more helpful for me since I am familiar with this two software.

You need to look at the Fourier transform method to evaluate hilbert transforms, as the Kronig Kramers transform is nothing but the Hilbert transform. Look it up. There's also a MATLAB function 'hilbert' for hilbert transform of discrete data.

I have used it myself and it works pretty well
 
singhvi said:
You need to look at the Fourier transform method to evaluate hilbert transforms, as the Kronig Kramers transform is nothing but the Hilbert transform. Look it up. There's also a MATLAB function 'hilbert' for hilbert transform of discrete data.

I have used it myself and it works pretty well

Many Thanks for your reply Singhvi,

Yes, KK relation is the Hilbert transform and no need to write complected program for KK relation in Matlab.

Cheers

Devnath
 
can you please give details of the steps you have taken to solve your problem. I am facing similar problem, I have n, k values and by using KK want to extrapolate to higher and especially lower energies.
thank
 
I want to evaluate refractive index from experimental data using KKR relation. As the data is limited to a finite spectrum, it is difficult to reduce errors related to infinite spectrum integration in KKR.

The calculated hilbert transform directly on 'absorption coefficient' data but it did not make any sense. Can you please elaborate on Hilbert transform in MATLAB to solve KKR relations.

Thanks,
Amin
 
That is the kind of stuff I get paid for. :) Can't just give out all the details of the program for free.
 
I have Absortion data vs wavelength. I want to evaluate the refractive index using MATLAB or origin but I did not success..I use hilbert transform but after that I don't know how to manage the refractive index from these data. Please help!
 

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